Topical deodorant formulations for use in controlling odour in the underarm area have been available in the market for many years, in solid stick or liquid form. Deodorant compositions have contained deodorizing active ingredients of several types. For example, antimicrobial agents function to inhibit bacterial growth, thus reducing bacterial interactions with sweat gland secretions, which are responsible for producing undesirable odours. Malodour masking agents such as perfumes and fragrances function to mask the malodours produced by bacterial interactions. Malodour neutralizers are also available which serve to chemically fix malodours. Thus, deodorant actives known in the art have generally referred to topical materials which inhibit the formation of, mask, or neutralize malodours resulting from perspiration.
Solid deodorant formulations of the prior art have commonly contained propylene glycol as the principal ingredient, and triclosan as a deodorizing active. The general manufacturing process for solid deodorants and cosmetics is also known. Deodorant formulations are typically mixed in relatively large quantities under heat, then poured into individual product containers, which act as molds to permit the sticks to be cast directly in them. Such product containers may be filled from the bottom or the top, and the deodorant stick may be shaped with a domed top or flat top.
A problem with many of the deodorant formulations that form part of the prior art is that they have relied on ingredients that have been found to be detrimental to human health or irritating to the skin. For instance, as substantiated by independent studies, a common deodorizing active material, triclosan, appears to be harmful to human skin and potentially carcinogenic. Another common and effective ingredient in deodorant formulations, propylene glycol, has been found to be irritating to many consumers with sensitive skin. As consumers become more conscious of the ingredients contained in personal care products such as deodorants, there has been rising demand for alternative formulations which are composed of ingredients that are naturally sourced or are formulated with minimal environmental impact, are not detrimental to human health, and which are mild when applied to skin and can therefore be used by a greater number of consumers, even those with sensitive skin.
In addition to the above needs in regard to deodorant formulations, a significant manufacturing issue with deodorant formulations that rely on natural ingredients and do not contain triclosan or propylene glycol is reduced stability and shelf life. When solid stick formulations are created, a problem frequently encountered has been the shrinking of the deodorant stick after it has been poured into the container. Natural deodorant formulations in particular have been plagued by the problem of the stick shrinking at ambient temperatures, such that the deodorant stick separates from the container wall. This problem with solid cosmetic formulations is known in the industry as “sweating”, whereby moisture from the solid deodorant stick formulation condenses on the surface of the stick, and ultimately evaporates. As it evaporates, the product shrinks back from the container edges and loses the original surface texture. This results in an unattractive and unsalable product with poor surface characteristics. It has been a significant and costly problem with many natural deodorant stick products.
The problem is believed to reside in the use of water and volatile alcohols in the natural deodorant formulation, which has arisen in prior art formulations, including those formulated to lack propylene glycol. When such ingredients form a significant portion of the solid formulation, it is difficult to prevent these ingredients from condensing out of the solid stick and evaporating. However, in formulating natural and substantially natural deodorant formulations in accordance with prior art teachings, it has been inevitable that the high percentage of water and volatile alcohols causes such stability problems.
What is needed is a solid stick deodorant formulation, that preferably contains all natural or naturally sourced ingredients, and is stable once formed into a deodorant stick product in a container.